An old scholar got a request from a wealthy man to wean his son away from his bad habits. Scholar accepted man's request and went to see his son. The scholar took boy for a stroll through garden. Suddenly scholar stopped and asked boy to pull out a tiny paint growing there. Obeying him boy held the plant between his thumb and forefinger and pulled it out. After walking a while the scholar asked boy to pull out a slightly bigger plant. This time boy pulled little harder and plant came out with its roots. "Now pull out that one", said the scholar pointing towards a bush. This time boy used all his strength to pull out the bush and as result bush came out. "Now take this one out", said the scholar indicating a guava tree. The boy grasped the tree trunk and tried to pull it out using all this strength but its wouldn't budge. Panting with the effort boy said, "It's impossible.""So is it with the bad habits", said the scholar. "When they are young it is easy to pull them out but when they take hold they cannot be uprooted."This talk with the scholar changed the boy's life forever. 
Don't wait for bad habits to grow in you, drop them while you have control over it else they will get control you. 